10_Secretory Pathway

Question 1

Which part of the Golgi complex is closest to the plasma membrane?

Answer 1

Trans-Golgi Network (TGN)

Question 2

What pathway of vesicle travel do COPII, COPI and Clathrin mediate?

Answer 2

COPII: ER to Golgi
COPI: Golgi to ER
Clathrin: Golgi to Endosome, PM to Endosome, and perhaps some others.

Question 3

What technique can be used to isolate different types of vesicles?

Answer 3

homogenization and differential centrifugation

Question 4

Which coat protein form polyhedral structures around vesicles?

Answer 4

Clathrin

Question 5

What type of microfilament to vesicles travel along in animal cells?

Answer 5

microtubules

Question 6

When COPII-coated vesicles uncoat and fuse with another, what do they form?

Answer 6

VTC (vesicular-tubular carriers)

Question 7

What supplies the energy for movement of VTCs along microtubules by motor proteins?

Answer 7

ATP

Question 8

Which vesicular coat is the G-protein Sar1 associated with?

Answer 8

COPII

Question 9

What are GEFs?

Answer 9

Guanine Nucleotide Exchange Factors; they activate monomeric small GTPases

Question 10

What does exchange of GDP for GTP allow Sar1 to insert into the membrane?

Answer 10

the amino end is exposed in GTP, and the hydrophobic N-terminus allows Sar1 to instert into the membrane

Question 11

Which proteins recognize Sar1/GTP and cargo vesicles, and are recruited to surround the vesicle? (discussing COPII-assembly)

Answer 11

Sec23/Sec24

and then Sec 13/Sec31

Question 12

Once the coated vesicle is formed, what triggers Sar1 to hydrolyze GTP? What is the effect of this?

Answer 12

curvature of the membrane

coat disassembles

Question 13

What do Rab proteins provide compartments with? Are they G-proteins?

Answer 13

identity, and yes

Question 14

What is the name of the protein pair that provides specificity to vesicle fusion?

Answer 14

SNARES

Question 15

What tethers the vesicle to the target membrane prior to docking and fusion?

Answer 15

Rab effector is the tethering protein, which recognizes the specific Rab-GTP on the vesicle and tethers it.

Question 16

What are the v-SNARES and t-SNARES involved in a synaptic vesicle and the neuronal plasma membrane?

Answer 16

v-SNARE: synaptobrevin

t-SNARES: Snap25 and syntaxin

Question 17

What is needed to unfold the SNARE complex after fusion of the vesicle?

Answer 17

energy (so, an ATPase)

Question 18

On which positions of the headgroup can phosphoinositides be phosphorylated?

Answer 18

3, 4, 5

Question 19

What do kinases and phosphatases do to phosphoinositide headgroups?

Answer 19

kinase: adds a P
phosphatase: removes a P

Question 20

Which phosphoinositide is enriched in the plasma membrane?

Answer 20

PI(4,5,)P2

Question 21

In which cellular compartment membrane is PI(4)P enriched?

Answer 21

Golgi complex

Question 22

What phosphoinositide is found abundantly in endosome membranes?

Answer 22

PI(3)P

Question 23

What is the GEF that allows for exchange of GDP for GTP in Sar1?

Answer 23

Sec12